The present invention relates to a flat type image display, and more particularly, to a lateral field emission display in which the cathode and anode are laterally arrayed, and a fabricating method thereof.
Currently, a flat type image display is under development as an image display for a wall-mounted television or an HDTV. As such a flat type display, there is a liquid crystal display, a plasma display panel and a field emission display. Among those, the field emission display attracts much attention due to its brighter screen and lower power consumption.
FIG. 1 illustrates a sectional view of a portion of a conventional vertical field emission display. Referring to the drawing, a plurality of cathodes 12 are formed in a stripe pattern on a glass substrate 11. A plurality of micro tips 14 for emitting a electron beam are formed in an array on the cathodes 12. An insulating layer 13 which encloses the micro tips 14 formed on the cathode 12. A plurality of gates 15 which are formed to the cathodes 12 are provided on the insulating layer 13 and have an aperture 16 across which an electric field is induced above each micro tip 14.
In a fabricating method of the vertical field emission display having such a structure, i.e., a process of forming a micro tip array of several tens of nm, a highly microscopic process in sub-micron units is required for an etching process in accordance with a tip size (radius) and a gate aperture size. Namely, if the sharpness of the micro tip is not uniformly maintained, there may be a problem in displaying a uniform image. Thus, the maintenance of uniformity throughout the fabricating process is necessary for obtaining uniform sharpness of the micro tip.
Also, in the vertical field emission display, it is difficult to establish a RGB (red, green and blue) alignment in a process of coating a fluorescent material. Proper alignment is necessary since electrons emitted due to an electric field effect formed on the micro tip hit the fluorescent material to emit light. Further, since the present display adopts a light transmitting method, a clear image can be seen only when the fluorescent material itself is thin, which causes difficulty in the fluorescent material coating process.
To overcome the above-referred defects, a conventional lateral field emission display as shown in FIG. 2 is suggested. Referring to FIG. 2, the display comprises a cathode 23 having sharp tips 23a of a wedge shape on a substrate 21, a gate 24 and a anode 25. The cathode 23, the gate 24 and the anode 25 are disposed in parallel at a set distance laterally on insulating layers 22a, 22b and 22c, respectively. The overhead view of a tip of the lateral field emission display is a triangular shape as shown in FIG. 3A.
The fabricating method of the lateral field emission display having such a structure will now be described.
The cathode 23 having the wedge-shaped micro tip 23a of FIG. 2 is formed by depositing metal for the cathode, gate and anode, respectively, after growing an insulating material on the substrate 21, and etching the deposition using a reactive ion etching method. Then, the gate 24 and the anode 25 are formed in the same way, and the grown insulating material is patterned by using them as a mask.
However, there is a limit in making the metal micro tip 23a sharp by using only the reactive ion etching method after the metal film is deposited as described above. That is, as shown in FIG. 3B, however the wedge is sharpened, the tip portion is a line 26, not a point. Thus, when a bias voltage is applied between the wedge-shaped micro tip 23a and the gate 24, the electric field effect cannot be highly obtained. Thus, the emission of electrons is small and leakage current increases due to stray electrons 27 since the anode 25 is disposed on the same plane as that of the wedge-shaped micro tip 23a. For this reason, the bias voltage applied to the gate should be relatively large, and a structure by which a flow of electrons can be concentrated is necessitated to facilitate the emission of the electrons with a low bias voltage.